Plouffe's "grand theft" crack referred to charges of larceny that Issa faced in 1972 after he allegedly stole a Maserati sports car. Issa claims the incident was a case of mistaken identity and the charges were later dropped.

The "arsonist/insurance swindler" insult referred to a 1982 fire at a Cleveland warehouse belonging to Issa's companies Quantum Enterprises and Steal Shopper. The fire was ruled suspicious and Issa collected an insurance payout, but he was not charged with any crime.

Issa called White House press spokesman Jay Carney a "paid liar" over the weekend. He also said low-level IRS employees in the Cincinnati office at the center of the scandal had been directed by Washington.

His Democratic counterpart on the committee, Rep. Elijah Cummings of Maryland, came out swinging about the latter claim.

"Chairman Issa’s reckless statements today are inconsistent with the findings of the inspector general, who spent more than a year conducting his investigation," Cummings said in a statement.

"Rather than lobbing unsubstantiated conclusions on national television for political reasons, we need to work in a bipartisan way to follow the facts where they lead and ensure that the IG’s recommendations are fully implemented."

Former Obama White House spokesman Robert Gibbs also came to Carney's defense. He claimed Issa was just politicizing the scandal.

"Republicans are on the verge of overplaying their hand publicly, and the American people will quickly lose interest on their side on this," Gibbs said on MSNBC's "Morning Joe."
Gibbs said voters want to see the IRS cleaned up, "but they understand that Darrell Issa is doing nothing more than politicizing this event."

"To throw around the words 'liar' and 'perjury' as easily as he did is shameful."

Gibbs, now a senior campaign adviser for Obama, insisted that Issa should put up or shut up. "If he's got information that these people lied, he should put it out there today," he said.

"If he doesn't have information that they lied, then he should call each of them up personally and apologize, because this kind of discourse is why people lose faith in their institutions.

"This is why people tune out from the back and forth in Washington because people throw around terms like this, and then in the next sentence, they can't even say with 100 percent authority that what they said the minute before or 10 seconds before is actually true," he added.

"It's a stunning thing. It's why five people in this town take Darrell Issa seriously," Gibbs said.

Issa called Carney a liar during an appearance on CNN's "State of the Union" on Sunday for insisting the targeting of conservative groups by the IRS was the work of "rogue" employees at an agency office in Cincinnati.

"Their paid liar, their spokesperson ... he's still making up things about what happens in calling this local rogue," Issa said.

"The reason [IRS official] Lois Lerner tried to take the Fifth [Amendment] is not because there is a rogue in Cincinnati, it's because this is a problem that was coordinated in all likelihood right out of Washington headquarters and we're getting to prove it," he added.

Lerner, who led the IRS division handling groups seeking tax-exempt status, declined to answer questions before the House Oversight Committee, citing her right against self-incrimination. But not before she insisted she was innocent of any wrongdoing.

CNN quoted a "source close to Issa" as saying the Republican thought Plouffe's comments were "below the belt."

Issa's spokesman, in a statement, said: "Looks like the chairman hit a nerve today. Hopefully President Obama follows Plouffe on Twitter and may finally see some information from a senior adviser about what's going on at the IRS."